Problem: On Saturday, Christopher's parents gave birth to twins and named them Tiffany and Michael. When they were first born, Tiffany weighed 6.86 pounds, and Michael weighed 8.49 pounds. How much did the babies weigh in total?
Explanation: To find the weights of the 2 babies, we need to add their weights together. Tiffany's weight + Michael's weight = total weight. ${6}$ ${8}$ ${6}$ ${8}$ ${4}$ ${9}$ ${+\vphantom{0}}$ ${5}$ ${3}$ ${5}$ ${1}$ Together, the babies weigh 15.35 pounds.